Subject: RE: VS: VS: [Sipping] FW: I-DACTION:draft-sawada-sipping-sip-offeranswer-01.txt (Comments 4 to 6)

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Mon, 26 Jun 2006 08:19:32 +0200

Hi, 

>>> that you should always offer (or answer) what *you* want the state
of 
>>> the session to be, to the extent that it is permitted. (There are 
>>> constraints - many for answerers, but also some for re-offerers in a
>>> dialog.)
>>> 
>> [CHH] Yes, but in some of the re-INVITE-without-SDP scenarios the UAS

>> is supposed to send an offer according to what the UAC (the one 
>> sending the empty re-INVITE) wants. So, the UAC has to assume the UAS

>> knows what the UAC wants
>>
>> What scenarios require a particular kind of behavior?
> 
>> [CHH] In some of the 3PCC scenaios, where the UAC assumes, in orde to
make the scenario work, that the UAS will send a certain type of offer
(in the 
>> 200 response). Again, in those cases I don't think it's about what
the one sending the offer wants - it's about what the one receiving the
offer 
>>wants...
>
>Precisely which scenarios do you mean. It is pretty crazy to expect
such behavior, but I am not too surprised if there are scenarios like
that.
>
>I think there are a cases that require a UAS to be psychic. (Those
related to REFER often feel that way. Dale has recently written
something on that.)

[CHH] It's quite a while since we discussed this, but hopefully those
who pushed for the specfic behavior can correct me if I'm wrong. The
scenario was something like the following:

User A receives an hold re-INVITE. Later (when some transfer functions
have taken place) user A receives an empty re-INVITE. Now, in order to
make things work, user A is supposed to un-hold the session and send an
SDP offer as for a new session - not simply return the SDP from the
previous offer/answer transaction.

Regards,

Christer

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---

From: Paul Kyzivat <[email-masked]>
Date: Mon, 26 Jun 2006 17:37:46 -0400

> previous offer/answer transaction.

This doesn't require User A to be psychic - only to keep stating its 
desires at each opportunity.

In this scenario I believe User A was *put on hold* - he didn't *want* 
to be on hold. So at each opportunity (like the offerless reinvite) it 
simply states what it wants - which is *not* to be on hold.

If, after A had been put on hold it decided to initiate its own hold 
action (perhaps because another call was received), then when the 
reinvite is received it might indeed specify SENDONLY. That wouldn't be 
what the sender of the reinvite wants to hear, but it is the current 
situation. (Of course when A decided to do it own hold it probably 
should have done its own reinvite specifying INACTIVE.)

	Paul